In general you can't get to this goal by buying a retail property off the MLS because if you could, everyone would buy them (i.e. demand would be high, supply would not increase and prices would go up)  Banks in general will finance around 80% of the fair market value of the property, so you need to pay 80% for a property worth 100%. 

I do it all myself so I didnt have to pay much other than for supplies, but I'm still in the high $30,000's to do it.

Does it include supplies, tile, countertops, appliances? 

The problem is trying to use a percentage of a moving target to supply needed cash that is very specific. 

Some of the outside on/off shut off valves for the water supply were "frozen"The roof has some missing shingles from wind damage and missing rubber gaskets around piping that protrudes through the roof which allows water to get inside the attic.This is a question for anybody who wants to chime in.What other due diligence should I be conducting for an off-market seller financed 6 unit apartment building that comes with an adjacent vacant parcel? 

I'd focus on a place without monthly fees (or with very low ones) that does provide ample training.

. ;)They are deductible, and it really does not matter what you call them - supplies, furnishings, maintenance, decorations. 

Assuming the supply lines don't need any modification besides adding the two sub meters you would probably be looking at around 300-400 for an install.

The current inventory here is quite low, 0.6 months of supply.

Here's a quick version of what's gone on: supply (particularly of condos) in Miami was up prior to Covid.